Microcirculation in cardiogenic shock: from scientific bystander to therapy target

Despite diagnostic and therapeutic improvements, mortality rates in patients with cardiogenic shock remain relatively high. Several studies showed that cardiogenic shock is associated with alterations in the microvascular circulation. These alterations may be reversed by extracorporeal support devices. A study by Munsterman and colleagues adds to the body of evidence showing that in patients deemed ready for discontinuing intra-aortic balloon pump (IABP) support, microcirculatory flow in small vessels increases after ceasing IABP therapy. This study not only highlights the need for optimal timing of weaning from IABP support but also supports recent findings that global hemodynamics do not necessarily result in changes of microvascular perfusion. All modalities of modern treatment in cardiogenic shock need to be evaluated for their effect on the microcirculation. Microcirculatory evaluations should be part of randomized controlled trial protocols. More effort is needed to improve outcomes and understand the microcirculation as a therapy target and not as a silent bystander.

colleagues [1], whose investigation of the micro circulation in patients with IABP was reported in the previous issue of Critical Care, have addressed an important topic.
In the last fi ve years, an important body of knowledge showing the pathophysiological importance of the microcirculation in the development of multiple organ failure in critically ill patients has been built up. Th is has been made possible because of the development of novel techniques to either directly visualize or indirectly evaluate microvascular perfusion [2]. In CS, micro vascular alterations have been observed, resulting in a decrease of vessel density, the proportion of perfused capillaries, or microvascular fl ow [3,4]. Diff erent treatment strategies, including pharmacological interventions and mechanical assist devices, may lead to microcirculatory improvement in CS [5][6][7].
In their article, Munsterman and colleagues show that in patients deemed ready for dis continuing IABP support, microcirculatory fl ow in small vessels increases after ceasing IABP therapy. Th e authors conclude that IABP impairs microvascular per fusion in hemo dynamically recovered patients. Th ese impor tant fi ndings not only highlight the need for optimal timing of weaning from IABP support but also demonstrate that global hemodynamics do not necessarily result in changes of microvascular perfusion [8,9]. In theory, IABP improves peak diastolic pressure and this may also translate into better microcirculation. Although suffi cient cardiac output and arterial pressure are prerequisites for adequate microvascular perfusion, their relationship is very complex. Changes in micro vascular vessel density and fl ow, their heterogeneity, autoregulation, and response to therapeutic interventions might be dissociated from systemic eff ects [2,9]. Furthermore, with the knowledge of the study by Munsterman and colleagues, it is obviously important to realize that, depending on the stage of the disease course, an intervention has diff erent eff ects on the microcirculation.
Modern therapy of CS consists of an adequate regime with revascularization, drug treatment, and mechanical support [10]. Although there is no question about the Abstract Despite diagnostic and therapeutic improvements, mortality rates in patients with cardiogenic shock remain relatively high. Several studies showed that cardiogenic shock is associated with alterations in the microvascular circulation. These alterations may be reversed by extracorporeal support devices. A study by Munsterman and colleagues adds to the body of evidence showing that in patients deemed ready for discontinuing intra-aortic balloon pump (IABP) support, microcirculatory fl ow in small vessels increases after ceasing IABP therapy. This study not only highlights the need for optimal timing of weaning from IABP support but also supports recent fi ndings that global hemodynamics do not necessarily result in changes of microvascular perfusion. All modalities of modern treatment in cardiogenic shock need to be evaluated for their eff ect on the microcirculation. Microcirculatory evaluations should be part of randomized controlled trial protocols. More eff ort is needed to improve outcomes and understand the microcirculation as a therapy target and not as a silent bystander.
survival advantage of early revascularization and its benefi cial consequences for the macrocirculation, there is no systematic study on its eff ects on microcirculation. However, revascularization reverses the spiral of progressive left ventricular dysfunction and therefore is understood to improve the microcirculation.
Diff erent drugs, particularly fl uids, vasopressors, inotropes, levosimendan, and vasodilators, infl uence the hemodynamics of patients with CS. Th e administration of fl uids in CS is based mainly on pathophysiological considerations and has not been studied in adequate randomized clinical trials. No data regarding fl uid adminis tration and microcirculatory changes in the setting of CS are available. Similar to fl uid administration, the choice of vasopressor and inotropic therapy is based mainly on individual experience and institutional policy; furthermore, this choice diff ers between guidelines. However, vasopressors might be able to stabilize the mean arterial pressure, but their use has negative consequences for the perfusion within microvasculature [11]. In small observatory studies, benefi cial eff ects on microcirculatory indices in CS have been described for levosimendan and nitro glycerin [5,12].
Owing to the lack of evidence for the use of IABP in CS after successful revascularisation of occluded infarct vessels, its role remains controversial. To date, there is no adequately powered randomized clinical trial available, and knowledge is based on observational trials or trials before the era of primary PCI. IABP support improves microvascular fl ow in unstable patients; however, diff er ent time points of the disease seem to be of importance [6,9]. Figure 1 summarizes therapeutic strategies aff ecting micro vascular perfusion in CS. All interventions should be evaluated for their eff ect at the microcirculatory level. Microcirculatory evaluations need to be part of randomized controlled trial protocols. Guiding inter-individual modern therapy of CS with in vivo visualization tools may allow a more specifi c and appropriate therapy regime and improve outcomes. More eff ort is needed to understand the microcirculation as a therapy target and not as a silent bystander.